function Circle(x, y) {
    this.x = x;
    this.y = y;
    this.r = 50;

    this.show = function () {
        strokeWeight(1);
        stroke(255);
        noFill();
        ellipse(this.x, this.y, this.r * 2, this.r * 2);
    };

    this.grow = function () {
        if(!this.edge()){
            this.r += 1;
        }
    };

    this.edge = function () {
        return this.x + this.r > width || this.x - this.r < 0 || this.y + this.r > height || this.y - this.r < 0;
    }
}